Automated Cooling Fan for Pi

#! /usr/bin/env python3
import os
import RPi.GPIO as GPIO
import time
import datetime
import sys

# 5 * * * * sudo python /home/pi/fan.py
# A crontab will run every hour and check the temp. If the temp is > 49 the script will start the fan
# until the temperature goes down to 28. When it does, the script will end, shutting down the fan as well.
# If the script executes again while a previous script is running, the latter will exit
# ... meaning the pi is in hell, and will never get below FAN_END value :P

# Configuration
FAN_PIN = 18    # Pin controlling the relay
FAN_START = 49  # Start the fan if temperature > 49C
FAN_END = 28    # Stop the fan if temperature < 28C

# Get manual action from command line
action = sys.argv.pop() if len(sys.argv) > 1 else None

def GPIOsetup():
    GPIO.setwarnings(False)
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(FAN_PIN, GPIO.OUT)

def fanON():
    GPIOsetup()
    GPIO.output(FAN_PIN, 0)  # Fan on (relay closed)

def fanOFF():
    GPIOsetup()
    GPIO.output(FAN_PIN, 1)  # Fan off (relay opened)
    GPIO.cleanup()

def get_temp_from_system():
    res = os.popen('vcgencmd measure_temp').readline()
    return res.replace("temp=", "").replace("'C\n", "")

def check_fan(pin):
    GPIOsetup()
    return GPIO.input(pin)

def run(pin):
    current_date = datetime.datetime.now()
    temp = float(get_temp_from_system())

    if temp >= FAN_START:
        print(f"{temp}C @ {current_date}")
        if check_fan(pin) == 1:  # Fan is OFF
            print('Fan is Off... Starting Fan')
            fanON()
        else:
            print('Fan is already ON')

    elif temp <= FAN_END:
        print(f"{temp}C @ {current_date}")
        if check_fan(pin) == 0:  # Fan is ON
            print('Fan is on... Shutting it Down')
            fanOFF()
            return 1  # Exit script, Pi has cooled down
        else:
            print('Fan is already OFF')

# Handle manual actions
if action == "on":
    print('Turning fan on')
    fanON()
    sys.exit(0)
elif action == "off":
    print('Turning fan off')
    fanOFF()
    sys.exit(0)

# First check if the script is already running by checking fan state
fan_state = check_fan(FAN_PIN)

if fan_state == 0:
    print('Fan is on, script must be running from another instance...')
    sys.exit(0)
else:
    temp = float(get_temp_from_system())

    if temp < FAN_START:
        print(f"Pi is operating under normal temperatures: {temp}C")
        sys.exit(0)
    else:
        try:
            while True:
                tmp = run(FAN_PIN)
                if tmp == 1:  # Fan turned off because the temperature dropped
                    break
                time.sleep(10)  # Sleep to prevent excessive CPU usage
        except KeyboardInterrupt:
            fanOFF()